Burner and method for detection of halogens

ABSTRACT

An improved burner and method of construction is disclosed for use in detecting halogen and halogen containing compounds. A ring of indium is coated on the inner surface of a secondary flame supporting structure. A primary flame supporting structure is located within the secondary flame supporting structure. The indium ring is coated over a palladium, gold or rhodium base coating deposited on the secondary flame supporting structure. The method of coating the indium ring is also disclosed.

United States Patent 15] 3,695,813 Griffith et al. [451 Oct. 3, 1972 [54] BURNER AND METHOD FOR trophotometric Detection Limits; Analyst Nov. 1969 DETECTION OF HALOGENS Vol. 94 pp. 1,033- 1,035 [72] Inventors: 2115: f s j ;%gg Primary Examiner-Edward G. Favors 0 Attorney-Paul R. Harder and Robert J. Steinmeyer [73] Assignee: Beckman Instruments, Inc. [22] Filed: NOV. 27, 1970 [57] ABS CT An improved burner and method of construction is [211 App! 93,337 disclosed for use in detecting halogen and halogen containing compounds. A ring of indium is coated on 52 U.S.Cl ..43l/126, 356/87 the inner Surface of a Secondary flame Supporting [51] lnt.Cl. ..F23j 7/00 \structm'e- A P m ry me supporting structure is 58 Field of Search ..431/4 79 126- 356/87 mated within the secmdary flame suppming structure. The indium ring is coated over a palladium, gold [56] References Cited or rhodium base coating deposited on the secondary OTHER PUBLICATIONS Herrmann & Gutsche: Improvement of Flame-Specflame supporting structure. The method of coating the indium ring is also disclosed.

4 Claims, 1 Drawing Figure will!! \mmlgr PATENTEDUCT 3 I972 3 6 95,813

INVENTORS PAUL A. GRIFFITH DAVID A. ROHRER BURNER AND METHOD FOR DETECTION OF HALOGENS This invention relates generally to the detection of halogen and halogen containing compounds and more particularly to a new and improved burner and process of making the burner for use in the detection of such compounds.

In U.S. Pat. No. 3,504,976 there is disclosed new and novel process and apparatus for the detection of halogens and halogen containing compounds. More specifically, there is disclosed a process and apparatus .whereby the halogen containing sample, in vapor or gas form, is passed over a heated indium surface where the sample reacts with the indium to form a volatile indium halide. These halides are burned ina flame which im' parts such energy to the indium halide as to cause them to photometrically radiate. Such radiation is spectrally unique to indium halides offering a distinctive means of detection both quantitatively andqualitatively with the ability to discriminate between interfering compounds. One of the advantages of the process and apparatus disclosed in the aforementioned U.S. Patent over the prior art Beilstein test is that the indium halides radiate at unique wavelengths making it possible to determine specifically which halide is present. The original Beilstein test although affording a degree of sensitivity to the halides did not provide detectable radiation specific thereto making it impossible to distinguish which halide was present.

In the aforementioned U.S. Patent the indium was deposited on a suitable substrate such as beryllium copper in the form of a loosely coiled spiral, a screen or a tube. The spiral, screenor tube was then supported on indentations within the second flame supporting structure above the primary flame or was suspended within the structure by a palladium wire.

While these structures have adequately servedtheir purpose, it has been found that the indium metal tends to ball with prolonged usage of the burner thereby affecting the sensitivity of the detector. Further, certain of these structures impede the flow of gas through the second flame supporting structure.

It is the primary object of this invention to provide a new and improved burner of the type disclosed in the aforementioned U.S. Patent and a method of depositing the indium onto the inner wall of the second flame supporting structure.

It is a further object of this invention to provide a burner for use in the determination of halogen compounds which offers improved structural stability, less resistance to gas flow, more uniform temperature and temperature gradient control of the indium and secondary flame and which provides greater freedom from interference from fewer emissions and more uniform distribution of the indium on a substrate.

The single FIGURE of the drawing illustrates a new and improved burner for use in the determination of halogen compounds.

Referring now to the drawing, there is illustrated a first flame supporting structure comprising a tube 11 having a tip 12 for supporting a primary flame 17. The tube 11 is adapted to be connected to a source of fuel gas such, for example, as hydrogen. A second flame supporting structure comprises a tube 14 which surrounds and encloses the tip 12 of tube 11 and is connected at its lower end to an inlet 15 adapted to be connected to a source of flame supporting gas such as air. Located on the inner surface of tube 14 just below tip 22 is an indium coating 23 in the form of a thin ring and is deposited over a thin metallic substrate of palladium, gold or rhodium. The sample to be tested for the presence of halogen or a halogen containing compound may be entrained into the primary flame 17 by any suitable means such as by adding the sample to either the fuel gas or the support gas. Other methods of entraining the sample, either liquid, gas or solid, into the flame, are disclosed in the aforementioned patent and the reference cited therein. If desired, the second flame supporting structure 14 and the secondary flame 18 may be surrounded by a chimney 20 having an inlet 21 for receiving a suitable combustion support gas such as air. The chimney 20 is preferably of Vycor or Pyrex to allow the radiant energy to pass therethrough. It is obvious, however, that if desired, the chimney 20 may be omitted.

The quantity of combustion supporting gas admitted to tube 14 is insufficient to allow complete combustion of the fuel gases in primary flame 17. The remaining hot fuel gases and the hot sample are passed over the indium and burned in the secondary flame as they escape from tube 14.

Turning now to the method of forming the indium ring 23 the tube 14, supporting the secondary flame, is preferably of a non-metallic construction such as Vycor, quartz or alumina oxide. It has been found highly advantageous to coat the indium over a thin film of palladium coated onto the inner surface of tube 14 although gold or rhodium may also be used, the process remaining the same.

The following process has been found to produce good results in coating the indium over a palladium film. A Vycor tube is dried in a light flame and the tip 22 dabbed into a drop of liquid bright palladium which was allowed to coat the area on the inner wall of the Vycor tube to form a ring of one-quarter to one-half inchdepth. Any liquid palladium adhering to the outer surface of the tube may be wiped therefrom. The liquid palladium is then allowed to air dry overnight to remove the volatiles and the tube placed in a cold oven and heated in air to 500C for about 20 minutes. A good, heavy uniform coating of palladium has resulted from this process. Indium metal is heated in an atmosphere free of oxidants until it just melts, i.e. at approximately C. The palladiurn coated tip of the Vycor tube is lightly heated and dipped into the molten indium and withdrawn. A smooth coating of indium will adhere to the palladium coating. Any indium adhering to the outer surface of the tube may be wiped therefrom. This coating is allowed to cool and, if desired, may be again lightly heated and shook to remove any unevenness which may occur in the indium coating. After cooling, the indium coated tube is utilized in the construction of the burner hereinbefore described.

It has been found that by coating the indium over a thin film of palladium at the end ofthe secondary flame supporting structure adjacent the tip thereof a uniform, even distribution of indium on the substrate is possible and there is no or little tendency of the indium to ball after prolonged usage of the burner. Gold and rhodium have also been used with similar results. The improved burner offers less resistance to the flow of gas through the secondary flame supporting structure, provides more uniform temperature and temperature gradient over the indium coating and greater control of the secondary flame.

What is claimed is:

l. A burner for use in the determination of halogen compounds comprising:

a first flame supporting structure having a tip for supporting a primary flame;

a second flame supporting structure having a tip for supporting a secondary flame, said second flame supporting structure extending beyond and surrounding the tip of said first flame supporting 5 compounds comprising:

a first flame supporting structure having a tip for supporting a flame;

a second flame supporting structure having a tip for supporting a flame, said second flame supporting structure formed of glass and extending beyond and surrounding said first flame supporting structure;

a thin coating of palladium deposited on the inner wall of said second flame supporting structure adjacent the tip thereof;

a thin coating of indium deposited over said palladimeans for supplying a fuel gas to said first flame supporting structure; and

means for supplying a support gas to said second flame supporting structure.

4. A burner according to claim 3 further comprising:

a radiant energy transparent chimney surrounding and extending beyond the tip of said second flame supporting structure; and

means for supplying a combustion support gas to said chimney. 

2. A burner according to claim 1 further comprising: a radiant energy transparent chimney surrounding said second flame supporting structure and extending beyond the tip thereof; and means for supplying a combustion support gas to said chimney.
 3. A burner for use in the determination of halogen compounds comprising: a first flame supporting structure having a tip for supporting a flame; a second flame supporting structure having a tip for supporting a flame, said second flame supporting structure formed of glass and extending beyond and surrounding said first flame supporting structure; a thin coating of palladium deposited on the inner wall of said second flame supporting structure adjacent the tip thereof; a thin coating of indium deposited over said palladium; means for supplying a fuel gas to said first flame supporting structure; and means for supplying a support gas to said second flame supporting structure.
 4. A burner according to claim 3 further comprising: a radiant energy transparent chimney surrounding and extending beyond the tip of said second flame supporting structure; and means for supplying a combustion support gas to said chimney. 